Question

Suppose we have an array of variable length, and I want to process it by chunks that are of a maximum length of 100, and do it in the minimum number of chunks. So for an array of length 241, it would be 3 sub arrays of sizes 41, 100, 100 (or 100, 100, 41).

curr_len = arr.length;
offset = curr_len%100;
doSomethingWithSubArray(arr.slice(offset))

for(j = offset; j <= curr_len; j = j+100){
    doSomethingWithSubArray(arr.slice(j,j+100))
}

I’m sure there are more elegant ways of doing this, possibly without the special case before the for loop. Any ideas?

Answer 1

I’d expect the last chunk to be of smaller size. The code then would be:

for (var i=0; i<arr.length; i+=100)
    doSomethingWithSubArray(arr.slice(i, 100));

This is exactly what my splitBy function does:

Array.prototype.splitBy = function(n) {
/* get: number of items per array
return: array of n-sized arrays with the items (last array may contain less then n) */
    for (var r=[], i=0; i<this.length; i+=n)
        r.push(this.slice(i, i+n));
    return r;
}

Then write only:

arr.splitBy(100).forEach(doSomethingWithSubArray);